SCORCHING temperatures are set to push electricity demand across NSW to their highest level in years, although with much of the state's industry still shut down for the summer holidays, power supply is expected to be uninterrupted.

That could change if bushfires threaten high-voltage transmission lines, which connect the power stations to Sydney's north and west to the city, as happened in Victoria's Black Saturday bushfires of 2009.

According to data compiled by the Australian Energy Markets Operator, NSW electricity demand will reach close to 13,000 megawatt hours on Tuesday.

List of current incidents from the NSW Rural Fire Service:

This is the highest level since February 2011, when it reached a record 14,744 megawatt hours and compares with Monday's peak demand of about 11,000 megawatt hours, recorded late in the afternoon.

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The closure last year of one of the state's two aluminium smelters, the Kurri Kurri smelter near Newcastle, has sliced power demand in NSW, leaving a large amount of reserve electricity generation capacity.

According to AEMO data, 14,461 megawatts of power generation capacity is available to meet demand on Tuesday, which will be boosted by potential supplies from Queensland and the Snowy Mountains. This will leave more than 3250 megawatts of excess capacity to meet any demand spikes or interruptions to supply.